This invention relates generally to a pressure transducer using strain gauge technology for sensing pressure change to produce an electrical signal related to such change and employing electronics for processing and amplifying the signal and more particularly to improved structure for packaging such sensors.
An example of a prior art pressure transducer using strain gauge technology for sensing pressure change of the type with which the invention is concerned is disclosed and claimed in U.S. Pat. No. 6,453,747, which issued Sep. 24, 2002 to the assignee of the present invention, the subject matter of which is incorporated herein by this reference. In that patent, a transducer is described having a tubular port fitting formed with a fluid receiving opening at one end and a closed, integrally formed diaphragm in at an opposite pedestal end. A support member having an apertured flat end wall is locked onto the pedestal end in a selected orientation; The aperture of the support member is in alignment with strain gauge sensor elements bonded to the diaphragm and a flexible circuit has a first lobe section for mounting electronic components bonded to the rigid, flat end surface of the support with an opening aligned with the aperture in the flat end wall. A second lobe section of the flexible circuit is placed on a seating surface of an adjacent inverted connector and terminals extending through apertures in the second lobe section are soldered to circuit pads on the flexible circuit. Wires are ultrasonically bonded both to the strain gauge sensor elements and to circuit pads on the first lobe section and encapsulated by silicone gel.
A cup-shaped EMC shield is received over the first lobe section and the connector is turned over bending the flexible circuit assembly into a U-shaped configuration with wall portions of the connector locking onto the support member. A metal housing is received over the connector applying a load to an O-ring gasket mounted between the housing and the connector with the housing welded to a support flange hermetically connected to the tubular port fitting. The EMC shield is provided with outwardly extending tabs which engage the inside wall of the housing to form an electrical connection therewith.
Although transducers made in accordance with the noted patent are highly effective and are widely used, it is desirable to lower the cost of producing such transducers to make them more economically feasible to use them on various applications and thus increase manufacturing volume with resulting savings in large volume manufacturing.
It is an object of the present invention to provide a reliable yet lower cost transducer than the prior art transducer noted above. Another object of the invention is the provision of a transducer which is more easily assembled. Yet another object of the invention is the provision of a transducer, particularly amenable for use with variously sized and shaped connector terminals.
Briefly described, in accordance with the invention, a tubular port fitting having a fluid receiving opening at one end and a closed, integrally formed diaphragm at an opposite pedestal end has an angular orientation feature and a locking feature for locking receipt of a support member in a selected angular orientation on the pedestal end. A radial extending mounting flange is hermetically welded to the port fitting to engage with the support member. The support member has an apertured flat end wall surface received on the diaphragm portion, the aperture being in alignment with strain gauge sensor elements glass bonded to the diaphragm portion. An electronic circuit comprising a suitable flexible circuit material or printed hard board for mounting electronic components, including an integrated circuit and landing zones for spring contact members. The circuit substrate is bonded to the rigid, flat end surface of the support member and formed with an opening aligned with the aperture in the flat surface. Wires are ultrasonically bonded both to the strain gauge sensor elements and to circuit pads on the bonded section of the flexible circuit assembly and then encapsulated by silicone gel.
A cover member is used to provide support for the spring contact members to position them for engagement with the landing zones of the circuit substrate. The spring elements are enclosed within longitudinally extending cavities in the cover member aligned with the landing zones when the cover is attached to the support member. An elastomer environmental seal or gasket member is enclosed in a circumferential groove in the surface of the cover member. A cup-shaped EMC shield is received in a chamber formed on one side of the cover member, the shield provided with tabs which extend outwardly through openings in the sidewall of the cover member beyond the outer periphery of the sidewall. The cover member is provided with wall portions which lock onto the support member. Electrical spring contact members received in the longitudinal cavities in the cover member have one end protruding from the cover member to enable engagement with connector terminal ends with the opposite ends received on respective landing zones.
A hexagonal metal housing member combined with the body of the connector by means of insert molding has bent portions of terminals acting as contact landing zones for electrical connection with the contact spring members disposed in the cover member. The EMC shield tabs are spring biased into electrical connection with the metal housing member and with the housing member and connector applying a selected load to the elastomer gasket member placed in the circumferential groove formed in the sidewall of the cover member, the housing being welded around its lower periphery to the support flange to form a fluid seal and to maintain the loading on the elastomer gasket member.
Additional objects, features and methods of the invention will be set forth in part in the description which follows and in part will be obvious from the description. The objects and advantages of the invention may be realized and attained by means of the instrumentalities, combinations and methods particularly pointed out in the appended claims.